Conventional Combustion Exit Presentation
Transcript of Conventional Combustion Exit Presentation
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Conventional Combustion Exit Presentation
Megan Karalus Mentor: Robyn Thomas
Technical Adviser: Priyank Saxena Group Manager: Anthony Batakis Functional Manager: Andy Luts
September 7th, 2012
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Agenda
• Carbon Formation Investigation and Mitigation
– Broad Goal: Literature Review, Modeling and Analysis • Conclusions and Recommendations • Acknowledgements • Summer in San Diego
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Brief History….
• Current production injector • No carbon deposition • Lacks mechanical robustness
Cutback
Carbon deposition
with natural gas
• New proposed design • Carbon deposits on the shroud
face.
Fuel
2020 Outer Air Swirler
Inner Air Swirler
Shroud Face
Conventional Dual Fuel Injectors
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Brief History…
Cutback
2020
Previous Natural Gas Paint Test in Mars 100 Engine
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Project Outline
• Broad Goal: develop knowledge base and methodology for troubleshooting carbon buildup on other injector designs. – Theory and Literature Review – Chemkin Modeling (equilibrium & detailed chemistry) – CFD Analysis
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Carbon Types
Analogy to Snow and Frost Formation “Gas phase nucleation yields snow [carbon black] and
heterogeneous nucleation on a substrate and subsequent growth gives frost [pyrocarbon]” (Bourrat)
Broad Goal: Theory / Chemkin / CFD
Carbon Black / Soot Pyrocarbon
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Carbon Black
Formation
Fuel
Crucial for Soot -> Pyrene
Controlling Parameters
• Pressure • Temperature • Residence Time • Higher Hydrocarbons • Equivalence Ratio
Broad Goal: Theory / Chemkin / CFD
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Pyrocarbon
Formation and Control
1. More likely than we think? "It is only in very exceptional circumstances that the interaction
of a hydrocarbon with a metal surface does not lead to carbon deposition.” [Bond 1997]
2. Forms at lower temperatures and or pressures than carbon black. “…a pyrocarbon should be formed at a lower T and (or) P than predicted by
classical homogeneous nucleation, which gives rise to the formation of carbon blacks.”
[Delhae 2001]
3. Surface plays a key role. "It has been shown that the substrate plays a role in the first pyrocarbon layers
from a physical (roughness, curvature and surface energy) and a chemical (nucleation sites) point of view.”
[Delhae 2001]
Broad Goal: Theory / Chemkin / CFD
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Chemkin Outline
1. Equilibrium 2. Perfectly Stirred Reactor 3. Opposed Flow Diffusion Flame
Broad Goal: Theory / Chemkin / CFD
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1. Equilibrium
Constant mixture temperature and pressure
Temperature and mixing near the shroud are controllable parameters in design of injectors.
What we learn…
• Temperature threshold for presence of carbon as a function of equivalence ratio.
• Carbon presence requires rich mixtures
Broad Goal: Theory / Chemkin / CFD
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2. PSR - Setup
Perfectly Stirred Reactor (PSR) • Parameter Study Method
– Hold constant Equivalence Ratio and Pressure.
– Vary Temperature and Residence Time.
PSR T, P, t
Fuel/Air
Φ
Products
Chemical Mechanism
Broad Goal: Theory / Chemkin / CFD
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2. PSR - Results
Equivalence Ratio = 2, P=250 psia What we learn… • Time allowed for reaction
can be important (residence time).
• Minimum temperature threshold as a function of residence time for carbon.
Broad Goal: Theory / Chemkin / CFD
Mol
e Fr
actio
n P
yren
e
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3. Opposed Flow Diffusion Flame
• Transport can be important. • Pyrene is produced at
higher temperatures but can exist at lower temperatures in rich mixtures.
0
500
1000
1500
2000
2500
3000
3500
0 0.2 0.4 0.6 0.8 1
Distance (cm)
Tem
pera
ture
(F)
-2.0E-12
-1.5E-12
-1.0E-12
-5.0E-13
0.0E+00
5.0E-13
1.0E-12
1.5E-12
2.0E-12
2.5E-12
Rat
e of
Pro
duct
ion
(mol
e/cm
3-s)
Temperature (F) ROP-A4
0
500
1000
1500
2000
2500
3000
3500
0 0.2 0.4 0.6 0.8 1
Distance (cm)
Tem
pera
ture
(F)
0.0E+00
5.0E-11
1.0E-10
1.5E-10
2.0E-10
2.5E-10
3.0E-10
3.5E-10
4.0E-10
4.5E-10
5.0E-10
Mol
e Fr
actio
n A
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Temperature (F) Mole Fraction A4
What we learn…
Production of Pyrene Location of Pyrene
Broad Goal: Theory / Chemkin / CFD
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3. Opposed Flow Diffusion Flame
• Transport can be important. • Carbon Black is formed
wherever Pyrene is present.
0
500
1000
1500
2000
2500
3000
3500
0 0.2 0.4 0.6 0.8 1
Distance (cm)
Tem
pera
ture
(F)
0.0E+00
5.0E-11
1.0E-10
1.5E-10
2.0E-10
2.5E-10
3.0E-10
3.5E-10
4.0E-10
4.5E-10
5.0E-10
Mol
e Fr
actio
n A
4
Temperature (F) Mole Fraction A4
0
500
1000
1500
2000
2500
3000
3500
0 0.2 0.4 0.6 0.8 1
Distance (cm)
Tem
pera
ture
(F)
0
2E-16
4E-16
6E-16
8E-16
1E-15
1.2E-15
1.4E-15
1.6E-15
1.8E-15
Rat
e of
Pro
duct
ion
of C
B
(g/c
m3-
s)
Temperature (F) ROP CB
What we learn… Broad Goal: Theory / Detailed Chemistry / CFD
Location of Pyrene Carbon Black Production
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3. Opposed Flow Diffusion Flame
• Transport can be important. • Pyrene is produced at
higher temperatures but can exist at lower temperatures in rich mixtures.
• Soot is formed wherever Pyrene is present.
• CO is a good ‘marker’ for the presence of Pyrene and therefore Carbon Black – useful for CFD analysis.
What we learn… Broad Goal: Theory / Detailed Chemistry / CFD
Co-Location of Pyrene and CO
0.0E+00
5.0E-03
1.0E-02
1.5E-02
2.0E-02
2.5E-02
3.0E-02
3.5E-02
4.0E-02
4.5E-02
5.0E-02
0 0.2 0.4 0.6 0.8 1
Distance (cm)
Mol
e Fr
actio
n C
O
0.0E+00
5.0E-11
1.0E-10
1.5E-10
2.0E-10
2.5E-10
3.0E-10
3.5E-10
4.0E-10
4.5E-10
5.0E-10
Mol
e Fr
actio
n A
4
Mole Fraction CO Mole Fraction A4
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CFD Outline
Assumption #1
Carbon Black (soot formation) is responsible for carbon deposition.
Assumption #2 Pyrocarbon is responsible for carbon deposition
(i.e. the surface participates)
Broad Goal: Theory / Chemkin / CFD
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CFD: Soot
Assumption #1
Carbon Black (soot formation) is responsible for carbon deposition.
Near Shroud
1. Formed in recirculation zone near shroud (i.e. PSR)?
2. Formed in flame and transported to shroud?
Broad Goal: Theory / Chemkin / CFD
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CFD: Soot
" Formed in recirculation zone near shroud (i.e. PSR)?
2. Formed in flame and transported to shroud?
Assumption #1
Carbon Black (soot formation) is responsible for carbon deposition.
Red is all greater than 5% CO Max
2020 Shroud
Broad Goal: Theory / Chemkin / CFD
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CFD: Soot
" Formed in recirculation zone near shroud (i.e. PSR)?
" Formed in flame and transported to shroud?
Broad Goal: Theory / Detailed Chemistry / CFD / Experiments
Assumption #1
Carbon Black (soot formation) is responsible for carbon deposition.
Red is all greater than 5% CO Max
2020 Shroud
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CFD: Pyrocarbon
Assumption #2 Pyrocarbon is responsible for carbon deposition
(i.e. the surface participates)
• On equilibrium model, plot conditions near shroud determined from CFD and paint tests
Injector Shroud Inner Air Swirler
Broad Goal: Theory / Chemkin / CFD
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Conclusions and Recommendations
• Rich mixtures are required for carbon formation (soot or pyrocarbon)
• Small amounts of higher hydrocarbons in the fuel will increase the likely hood of soot formation
• Increased pressure allows formation of soot precursors at lower pressures and shorter residence times.
• The nucleation of soot is not temperature dependent.
• CO is a good marker species for soot in CFD models.
• Carbon deposition is most likely due to ‘pyrocarbon’ (the surface participates)
• Apply equilibrium model in conjunction with CFD as a potential pass/fail design tool for other injectors.
• Determine if paint application is influencing test results (SI Rig test)
Conclusions Recommendations
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Acknowledgements
• Tony Batakis • Robyn Thomas • Priyank Saxena • Ryan Youtsey • Dan Golden • Stuart Greenwood • Mike Lane • Emily Almaraz • Jeff Detweiler • Scott Lindner
• Paul Cramer • Barry Raghunathan • Jack Johnson • Will Rhodes • Charmaine Gary • Denise Rodriguez • Andy Luts • Tim Bridgman • Rotations • Interns